Methanol oxidation on Cu(110)

Francis, S.M.; Leibsle, F.M.; Haq, S.; Xiang, N.; Bowker, Michael

doi:10.1016/0039-6028(94)90132-5

Cited by 163 publications

(130 citation statements)

References 24 publications

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“…2CO 2 þ H 2 þ 2e À These steps are similar to those proposed earlier for methanol reaction with Cu [20] and ZnO [21,22]. Note that for copper, oxygen has to be present on the surface first, before methanol can react to make the formate; not only is it a reactant, but the oxygen also promotes the reactivity, due to its basic character.…”

Section: The Mechanism Of Methanol Oxidation On Au/tiomentioning

confidence: 75%

Methanol oxidation on Au/TiO2 catalysts

et al. 2007

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We have investigated the adsorption and reaction of methanol with Au/TiO 2 catalysts using a pulsed flow reactor, DRIFTS and TPD. The TiO 2 (P25) surface adsorbed a full monolayer of methanol, much of it in a dissociative manner, forming methoxy groups associated with the cationic sites, and hydroxyl groups at the anions. The methoxy is relatively stable until 250°C, at which point decomposition occurs, producing mainly dimethyl ether by a bimolecular surface reaction. As the concentration of methoxy on the surface diminishes, so the mechanism reverts to a de-oxygenation pathway, producing mainly methane and water (at $330°C in TPD), but also with some coincident CO and hydrogen. Au catalysts were prepared by the deposition-precipitation method to give Au loadings between 0.5-3 wt %. The effect of low levels of Au on the reactivity is marked. The pathway which gives methane, which is characteristic of titania, remains, but a new feature of the reaction is the evolution of CO 2 and H 2 at lower temperature (a peak is seen in TPD at 220°C), and the elimination of the DME-producing state. Clearly this is associated with the presence of Au and appears to be due to the production of a formate species on the surface of the Au component. This formate species is mainly involved in the reaction of methanol with the Au/TiO 2 catalysts which results in a combustion pathway being followed, with complete conversion occurring by $130°C.

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Section: The Mechanism Of Methanol Oxidation On Au/tiomentioning

confidence: 75%

Methanol oxidation on Au/TiO2 catalysts

et al. 2007

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“…Coadsorption of methanol and oxygen at 300 K and 10 -7 mbar was found to lead to a (5x2) ordered ad-structure of methoxy on Cu(110). 9,28,34 Depending on the mixing ratio and on the adsorption time either a pure (5x2) pattern or a (5x2) layer coexisting with an (2x1)-O structure develops. Increasing the total pressure to 10 -5 mbar causes the transformation into a c(2x2) structure.…”

Section: Reaction Intermediates and Characterization In Xpsmentioning

confidence: 99%

“…9,35,46 Even at coverages below that of the high coverage phases, i. e. at the θ O =0.5 of a (2x1)-0 structure the reactivity is already strongly reduced. A straightforward explanation was provided by STM experiments showing that only the terminal oxygen atoms of the O-Cu-O chains forming the (2x1)-O are reactive towards adsorbed methanol.…”

Section: Role Of Oxygenmentioning

confidence: 99%

“…[7][8][9][10][11][12][13][14][15][16] Different in situ techniques were applied in order to identify the active surface phases on polycrystalline Cu at higher pressure (mbar range). [17][18][19][20][21][22][23][24][25][26] Cu(110) surfaces were investigated with temperatureprogrammed desorption (TPD), molecular beam techniques, low energy electron diffraction (LEED), x-ray photoelectron spectroscopy (XPS) and scanning tunnelling microscopy (STM).…”

Section: Introductionmentioning

confidence: 99%

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Adsorbate coverages and surface reactivity in methanol oxidation over Cu(110): An in situ photoelectron spectroscopy study

Günther

Zhou

Hävecker

et al. 2006

The Journal of Chemical Physics

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The adsorbate species present during partial oxidation of methanol on a Cu(110) surface have been investigated in the 10 -5 mbar range with in situ x-ray photoelectron spectroscopy (XPS) and rate measurements. Two reaction intermediates were identified, methoxy with a C 1s binding energy (BE) of 285.4 eV and formate with a C 1s BE of 287.7 eV. The c(2x2) overlayer formed under reaction conditions is assigned to formate. Two states of adsorbed oxygen were found characterized by O 1s BE's of 529.6 and 528.9 eV, respectively. On the inactive surface present at low T around 300 -350 K formate dominates while methoxy is almost absent. Ignition of the reaction correlates with a decreasing formate coverage. A large hysteresis of ≈ 200 K width occurs in T-cycling experiments whose correlation with adsorbate species was studied with varying oxygen and methanol partial pressures. The two branches of the hysteresis differ mainly in the amount of adsorbed oxygen, the methoxy species and a carbonaceous species. Methoxy covers only a minor part of the catalytic surface reaching at most 20%. Above 650 K the surface is largely adsorbate free.

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“…Francis et al (1994) reported the reduction of Cu 2 O by heating in methanol vapor (forming methoxy, CH 3 O, which decomposes to form gaseous CO and CO 2 ). In our experiments it was found that heating to ϳ350°C in ϳ5.10 -5 Torr methanol vapor also resulted in decomposition of the oxide to below the limits of detection.…”

Section: Sample Preparationmentioning

confidence: 98%